158 



THE DESEADO FORMATION OF PATAGONIA 



Still other forms like Amblypoda and Arsinotherium have 

 been suggested as having characters in common with 

 Pyrotherium, and it is clear that, with such a variety of 

 forms, some of the characters must be parallelisms due 

 to a common adaptation, and only one of these varied 

 groups can be the one to which Pyrotherium is related. 

 For myself, I have made comparisons with the Amblypoda 

 and Arsinotherium, and feel that such features as the mas- 

 sive limbs, shape of individual bones, etc., are due simply 

 to the fact that all these are massive animals. In the 

 case of Arsinotherium, there are some characters which 

 are also common to hyracoids and elephants, like the 

 position of various basicranial foramena, the prolongation 

 backward of the jugal and the shape of the palatines. 

 My conclusion is that Pyrotherium is related to the pro- 

 boscideans, and came from the same stock which gave 

 rise to hyracoids, elephants and Arsinotherium. I think 

 further that Pyrotherium belongs definitely to the pro- 

 boscidean line. 



Referring back to the foregoing table. The develop- 

 ment of tushes may be an adaptive character; but in the 

 elepnants it is inc. 2 of the upper and inc. 2 of the lower 



